Potato poisoning occurs when someone eats the green tubers or new sprouts of the potato plant.
Solanine (very toxic even in small amounts)
The poison is found throughout the plant, but especially in green potatoes and new sprouts. Never eat potatoes that are spoiled or green below the skin. Always throw away the sprouts.
Potatoes that are not green and have had any sprouts removed are safe to eat.
Pelmer M, Bitz J. Plants. In: Hoffman RS, Goldfrank LR, Flomenbaum NE, et al., eds. Goldfrank's Toxicologic Emergencies. 7th ed. New York, NY: McGraw-Hill; 2002:chap 78.